The present invention relates to an improved proportional linear output system for transferring displacement on a reduced or an enlarged scale, which works as a mechanism to transfer displacement of a positioning apparatus.
FIG. 1 illustrates a conventional proportional linear output system (refer to Japanese Patent Laid-Open No. 52-9462). According to this system, when an input displacement is applied to a point P, a lever L.sub.1 made of a rigid member (which does not develop elastic deformation) rotates with a fulcrum O as a center to produce displacement of a first step on a contracted scale. Further, the displacement at a point Q is contracted by a lever L.sub.2 which rotates with a fulcrum S as a center, so that a reduced output displacement is produced at a point R. However, since the input and output displacements undergo rectilinear motion owing to a rectilinearly moving table, positions for transferring displacements at points P, Q and R undergo the changes with the turn of the levers. Consequently, linearity in the output displacement is lost with the turn of the levers, making it difficult to highly precisely maintain a relation of input and output over a wide range of movement.
There has also been proposed a proportional linear output system as shown in FIG. 2 (refer to Japanese Patent Publication No. 38-19032). According to this system, a lever L.sub.3 consists of a resilient member and, when an input displacement is given to a point G, a displacement is obtained which is reduced by the principle of a lever and by the elastic deformation. This system, however, presents poor linearity and is not suited for attaining the positioning with high accuracy, although it can be used for small displacements.
Thus, with the conventional proportional linear output systems which are simply based upon the principle of levers, the displacement is reduced depending upon a lever ratio. According to the conventional systems, therefore, the reduction lever undergoes arcuate motion and a point of application of force between an input/output point and the lever undergoes the change with the turn of the lever, causing the linear characteristics to be diminished. Consequently, accuracy is diminished when the positioning is carried out over a wide range.